Parameter Types
Parameters may be defined as "read-only" or "read-write". "Read-only" parameters are used to
provide status or identifying information to the DTE, but cannot be set by the DTE;
attempting to set their value is an error. In some cases (specified in the description of the
individual parameter), the modem may ignore attempts to set the value of such parameters
rather than respond with an ERROR result code, if the continued correct operation of the
interface between the modem and DTE will not be affected by such action. Read-only
parameters may be read and tested.
"Read-write" parameters may be set by the DTE, to store a value or values for later use. Readwrite
parameters may be set, read, and tested.
Parameters may take either a single value, or multiple (compound) values. Each value may be
either numeric or string; the definition of the parameter will specify the type of value for each
sub parameter. Attempting to store a string value in a numeric parameter, or a numeric value in
a string parameter, is an error.
Parameter Set Command Syntax
The definition of the parameter indicates, for each value, whether the specification of that
value is mandatory or optional. For optional values, the definition indicates the assumed
(default) value if none is specified; the assumed value may be either a previous value (i.e., the
value of an omitted sub parameter retains its previous value), or a fixed value (e.g., the value
of an omitted sub parameter is assumed to be zero). Generally, the default value for numeric
parameters is 0, and the default value for string parameters is "" (empty string).
The following syntax is used for parameters that accept a single value:
+<name>=[<value>]
The following syntax is used for parameters that accept more than one value:
+<name>=[<compound_value>]
For each implemented parameter, if all mandatory values are specified, and all values are
valid according to the definition of the parameter, the specified values are stored. If <name>
is not recognized, one or more mandatory values are omitted, or one or more values are of the
wrong type or outside the permitted range, the modem issues the ERROR result code and
terminates processing of the command line. An ERROR is also generated if too many values
are specified. In case of an error, all previous values of the parameter are unaffected.
Parameter Read Command Syntax
The DTE may determine the current value or values stored in a parameter by using the following syntax:
+<name>?
The modem responds by sending the current values stored for the parameter to the DTE in an
information text response. The format of this response is described in the definition of the
parameter. Generally, the values are sent in the same form in which they would be issued by
the DTE in a parameter setting command; if multiple values are supported, they will generally
be separated by commas, as in a parameter setting command.
Parameter Test Command Syntax
The DTE may test if a parameter is implemented in the modem, and determine the supported
values, by using the syntax:
+<name>=?
If the modem does not recognize the indicated name, it returns an ERROR result code and
terminates processing of the command line. If the modem does recognize the parameter name,
it returns an information text response to the DTE, followed by an OK result code. The
information text response indicates the values supported by the modem for each such
sub parameter, and possibly additional information. The format of this information text is
defined for each parameter.
2.4.5 Additional Syntax Rules
Concatenating Commands after Extended Syntax Commands
